A solution prepared by dissolving a 2.50 g sample of an unknown compound dissolved in 34.0 g of benzene, ${\mathrm{C}}_6{\mathrm{H}}_6$, boils 1.38° C higher than pure benzene. Which expression gives the molar mass of the unknown compound?

Compound	${\mathrm{K}}_{\mathrm{b}}$
${\mathrm{C}}_6{\mathrm{H}}_6$	${2.53}^{\circ }\mathrm{C}.{\mathrm{m}}^{-1}$